Some Observations on Steam-Engines, 117 



whether working single or double ; the load per square inch in 

 cylinder ; length of stroke in the cylinder ; the number of pump 

 lifts; the depth in fathoms of each lift; diameter of pumps in 

 inches ; time worked ; consumption of coals, in bushels ; num- 

 ber of strokes during the time ; length of stroke in pump; load 

 in pounds ; pounds lifted one foot high by a bushel of coals ; 

 number of strokes per minute; and lastly, a column for names 

 of engineers, and remarks. 



Messrs. Thomas and John Lean were appointed to the general 

 superintendance ; and the different proprietors, as also the re- 

 gular engineers of the respective mines, engaged to give them 

 every facility and assistance in their power. Their first monthly 

 report was for August 1811, and included eight engines, which 

 had in that month consumed 23,661 bushels of coals, and lifted 

 126,126,000 pounds of water one foot high, being an average 

 duty of 15,760,000 pounds lifted one foot high with each bushel 

 of coals. In the months of September and October the engines 

 reported were nine, and in November and December twelve ; and 

 it now evidently appeared that the regular publication of Messrs, 

 Leans' very useful Tables had already been attended by some 

 improvements in the condition of the engines ; for the average 

 duty for December 1811, extracted from these tables, appears 

 to have been 17,075,000 pounds. 



In January 1812 the number of engines reported was 14, 

 and by the end of that year they were increased to 19; and the 

 -average duty performed by all the engines in the last-mentioned 

 month had advanced to 18,200,000. 



In 1813 the number of engines included in the monthly re- 

 ports continued to increase till in December they were 29, and 

 the average work 20,162,000. 



During some of the montiis of 1814 the engines reported 

 were 32, and the average duty performed during December was 

 19,784,000 pounds Ufted one foot high with each bushel of coals. 

 The Table which is subjoined is an abstract froni Messrs. 

 Leans' Reports, and has been formed by first counting how maaiy 

 engines are reported, as in January 1815, 32 engines ; then 

 adding up the column containing the quantity of coals consumed 

 by all the engines during the month, and putting down the 

 amount, 1 10,S24; in like manner adding up the column of pounds 

 lifted l)y each engine one foot hiiih by one bushel of coals, the 

 amount of which was 637,320,9!H) ; and lastly, dividing the latter 

 quantity by 32, the number of engines at work, to obtain the 

 jiverage duty performed, viz. 19,916,250 pounds. 



H 3 Table 



